ascending pathways - spinocerebellar tracrs

Question 1

NON-CONSCIOUS PROPRIOCEPTION

Answer 1

Information from skin, muscles & joints to the cerebellum
for coordination of movement
1. Posterior spinocerebellar tract (trunk & LL)
2. Cuneocerebellar tract (trunk & UL equivalent)
3. Anterior spinocerebellar tract (trunk & LL)
4. Rostral spinocerebellar tract (UL equivalent)

Question 2

Posterior spinocerebellar tract (fibres enter C8 & below)

Answer 2

Collaterals of dorsal column afferent fibres
Synapse with the 2nd order neuron in Clarke’s nucleus C8-L2 (Fibres entering below L2 ascend in fasciculus gracilis until L2)
happens all on same side eg. L leg > Lft spinal cord

Question 3

clarke’s nucleus

Answer 3

integrates afferent information from proprioceptors and skin receptors
- summarise and sends to cerebellum

Question 4

2. Cuneocerebellar tract (fibres C7 & above)

Answer 4

= UL equivalent of posterior spinocerebellar
There is no Clarke’s nucleus - 1st order neurons ascend in fasciculus cuneatus
- synapse in accessory (lateral) cuneate nucleus in medulla

Question 5

3. Anterior spinocerebellar tract (LL) contralateral

Answer 5

2nd order neuron cell bodies are on the lateral surface of the ventral horn!!
• Spinal border cells in lumbar segments
• Afferents = muscles, skin, interneurons & descending tracts (feedback on intended movement)
• Decussate then ascend as anterior spinocerebellar tract
• Superior cerebellar peduncle to cerebellum
• Decussate again back to original side

Question 6

4. Rostral spinocerebellar tract

Answer 6

• UL equivalent of anterior spinocerebellar

Question 7

3 main ascending somatosensory pathways from the BODY:

Answer 7

Reach consciousness and 3 neurons
1. Anterolateral (spinothalamic) 
2. Dorsal column – medial lemniscus pathway 
Subconsicous lvl and 2 neurons:
3. Spinocerebellar pathways

Question 8

3 ascending somatosensory pathways from the HEAD:

Answer 8

1. Spinal trigeminothalamic pathway (3)
2. Chief sensory trigeminothalamic pathway (3)
3. Mesencephalic trigeminothalamic pathway (2)

Question 9

Trigeminal nuclei:

Answer 9

Trigeminal nuclei: 3 sensory + 1 motor

Question 10

3 trigeminothalamic pathways:

Answer 10

Mesencephalic = subconscious proprioception (midbrain)
Chief sensory = discriminative touch, pressure,
conscious proprioception (@ [pons lvl, lateral 2 motor)
Spinal = nociception & temperature (midpons > C3)

Question 11

SPINAL TRIGEMINOTHALAMIC - (3 neurons)

nociception & temperature

Answer 11

• Free nerve endings
• A delta & C fibres
• 1st order neuron cell body in trigeminal ganglion
• 1st order neuron enters pons & descends* to spinal
nucleus
• 2nd order neuron cell body in spinal nucleus (pons,
medulla, Cervical spine – extends to C3)
• Blends with substantia gelatinosa & dorsolateral tract
• 2nd order neurons decussate & join anterolateral tract
• Synapses in VPM thalamus + collaterals to brainstem
• 3rd order neuron ascends via posterior limb internal
capsule
• Post central gyrus, parietal lobe

Question 12

CHIEF SENSORY TRIGEMINOTHALAMIC - (3 neurons)

Discriminative touch & conscious proprioception

Answer 12

• Skin, proprioceptors & mechanoreceptors from muscles of mastication, facial & extraocular; TMJ; periodontal ligaments
• 1st order neuron cell body in trigeminal ganglion
• 2nd order neuron cell body in chief sensory nucleus
(pons)
• Most 2nd order neurons decussate & join medial
lemniscus
• Synapse in VPM thalamus
• 3rd order neuron ascends via posterior limb
internal capsule
• Post central gyrus, parietal lobe

Question 13

MESENCEPHALIC TRIGEMINOTHALAMIC

(2 neurons) non-conscious proprioception

Answer 13

proprioceptors, mechanoreceptors from muscles of mastication, gums, teeth hard palate
• 1st order neuron cell body in mesencephalic nucleus (midbrain)!!
• Sends processes to:
• ipsilateral cerebellum via superior cerebellar peduncle
• Trigeminal motor nucleus (reflexes)
• Brainstem reticular formation